A LATCH

Abstract: A latch comprises a support block (1) which, in use, is attached to a first member (2), and a strike block (5) which, in use, is attached to a second member (6). A first lever (3) is attached to the support block (1) and shaped to engage with the strike block (5) when the first (2) and second (6) members come into contact. A link member (9) is pivotally attached to the support block (1). A second level (10) is pivotally attached to the link member (9) and is shaped to engage with the strike block (5), with a third lever (11), pivotally attached to the link member (9) and engageable with the support block (1), to retain the latch in a latched position. Biasing means (15) biases the third lever (11) into engagement with the support block (1) when the second lever (10) is in its engaged position.

Description: A LATCH This invention relates to latches of the type used to latch together two parts of an item, such as the lid and body of a container. There are many forms of latch which have been used for a number of years for closing and sealing functions. Such latches, whilst being cheap and simple to manufacture often have the problem that they require manual operation to be closed and do not provide an indication to the user when they are not in a fully latched state. An example of such a latch would be the toggle type which comprises a first lever attached to an item, and a second lever which pivots on the first lever, engages with a latching surface, and locks in an over-centre pivot action. Such latches are cheap to manufacture, simple to use and reliable even in harsh environments. These latches do, however, have the problem that it is difficult to determine when they are securely latched and that they can, occasionally, be jarred open by vibrations. Attempts have been made to overcome these problems by provision of either a slide type secondary lock with a catch moving axially in the latch's lever, or by a spring catch type mechanism, where a steel latch engages from the base through the lever to latch. Both of these solutions can suffer from corrosion or jamming from dirt entering the mechanism and often have a "cheap" feel to their operation. Automatically closing latches are also available, but do not generally provide a strongly sealed closure and are vibration sensitive. There is a need therefore for a latch which closes automatically to provide a safe and secure closure but which may also provide a tight, vibration resistant closure. There is also a need to provide a latch which provides an indication that it is fully closed. According to a first aspect of the present invention a latch comprises: a support block which, in use, is attached to a first member; a strike block which, in use, is attached to a second member; a first lever attached to the support block and shaped to engage with the strike block when the first and second members come into contact; a link member, pivotally attached to the support block; a second lever, pivotally attached to the link member and shaped to engage with the strike block; a third lever, pivotally attached to the link member and engagable with the support block, to retain the latch in a latched position; and, biasing means for biasing the third lever into engagement with the support block when the second lever is in its engaged position. Because the first lever automatically engages with the strike block, the two members will be latched even if the user does not bring the second lever into engagement, thus ensuring that the item is always safely fastened on engagement of the two members. Also, as the third lever is biased into engagement with the support block, the latch will not be jarred free by vibration or accidental snagging and, since the third lever must be depressed prior to the latch being released, accidental opening of the latch is unlikely. The strike block may comprise two components, the first of which engages with the first lever, and the second of which is adjustably mounted on the first to provide an adjustable engagement with the second lever. The biasing means may be a spring or a combination of springs, and may also act to bias the second lever into a warning position when it is not fully engaged and/or bias the first lever towards an engaging position. According to a second aspect of the present invention a latch comprises: a support block which, in use, is attached to a first member; a first lever, pivotally connected to the support block; a second lever, pivotally mounted on the first lever and arranged to engage a second member releasably; a third lever, pivotally mounted on the first lever, and arranged to engage the support block releasably; and, biasing means for biasing the third lever towards the position in which it engages another part of the latch when the second lever is in an engaged position. The third lever may engage with the support block, or, alternatively can engage with the second lever to provide a locking function. The first and third levers may be mounted on a common axis. The second lever is preferably biased to a position in which it "flags" the fact that the latch is not engaged, ie the free end of the second lever projects outwardly from the latch. Preferably, the third lever is arranged so that it provides an indication to a user when fully engaged with the support block or may protrude through the second lever and engage with it. Advantageously, there is a common biasing means for the second lever and the third lever. The biasing means will usually be a spring, which can be attached to the support block or first lever at one end and attached to the third lever at its other end. The biasing means may, however, be a torsion spring attached to the third lever and in engagement with the first lever, the second lever or support block to bias the third lever toward an engaged position. Because the third lever engages with the support block when the latch is in a closed position, the latch provides a more secure fixing, which is less likely to become disengaged during excessive vibration of the latch assembly. Also, as the third lever must be released before the latch will disengage, there is a reduced possibility of the latch being opened accidentally. Furthermore, as the third lever provides an indication of whether or not the latch is fully engaged, the assembly is less likely to be left accidentally in a partially engaged position. Examples of a latches according to the present invention will now be described with reference to the accompanying drawings in which: Fig. l is a diagram showing a first example latch in a released position; Fig. 2 is a diagram showing the first example latch in a partially closed position; , . Fig. 3 is a diagram showing the first example latch in a partially closed, but not fully engaged position; Fig. 4 is a diagram showing the first example latch in a fully engaged position; Fig. 5 is a diagram showing a second example latch in a disengaged position; Fig. 6 is a diagram showing the second example latch prior to engagement; Fig. 7 is a diagram showing the second example latch in an engaged, but not fully latched, position; Fig. 8 is a diagram showing the second example latch in the fully closed position; Figs. 9A and 9B are diagrams showing alternative spring arrangements for the second example latch; and, Figs. 10A, 10B and IOC are diagrams showing the second example latch with alternative third lever engagement with a second lever; Figs. HA and 11B are diagrams showing plan and side views of a third example latch in a fully engaged position; and, Figs. 12A and 12B are side views of the third example latch in partially engaged positions. Referring to figure 1, a support block 1 is attached to a first member 2 which forms part of the item to be latched. Attached to the support block 1 is a first lever 3 which is shaped at one end to engage with a hook portion 014 item to be latched, and which comprises two components 4,7. The first of these components 4 comprises a hook and engages with the first lever 3 and the second component 7 is adjustably connected via a bolt 8 to the 4 and can be used to adjust the tightness of the seal provided by the latch. The first lever 3 and the hook 4 are arranged so that, when the two members 2,6 are brought into engagement, the first lever 3 rides over the hook 4 and latches to it. Pivotally connected to the support block 1 are two link members 9, and pivotally connected to these two link members 9 are a second lever 10 and a third lever 11. One end 12 of the second lever 10 is shaped so that, when the latch is in a fully closed position, it engages with the component 7 of the strike block 5 to provide a tight, sealed closure as will be described below. When the first lever 3 has engaged with the strike block 5, the second lever 10 is urged to protrude outwards by the action of a biasing spring 15 via the third lever 11, which rests in a recess 16 in the second lever 11 and engages with it to rotate the second lever 10 in a direction away from the strike block 5, providing an indication to a user that the latch is not fully closed. Rotation of the second lever 10 toward the strike block 5 also rotates the third lever 11, as the second and third levers 10,11 engage with each other, and brings a hooked end 13 of the third lever 11 into a position above a lip 14 on the support block 1 (see figure 3) . The link members 9 provide an over-centre pivot action similar to that of a toggle latch of the type described above. To fully close the latch, a user then applies pressure to the pivotally connected end 17 of second lever 10 and/or the third lever 11 to engage the hooked end 13 with the lip 14 (see figure 4) . The biasing spring 15 connected to the third lever 11 and the first lever 3 retains the hooked end 13 on the lip 14 to prevent accidental release of the latch. The third lever 11 protrudes through an opening in the second lever 10, and to release the latch a user depresses the third lever 11 to disengage the hooked end 13 and the lip 14. The pivotally connected end 17 of second lever 10 is then pulled away from the first member 2 and can be brought back into the position shown in figure 2 by rotation of the end 12 of the second lever 10 away from the strike block 5. Further rotation of the second lever 10 in the same direction urges the hooked end 13 of the third lever 11 onto the end of the first lever 3, which is then caused to move and disengage from the strike block 5. The strike block component 7 is adjustable so that a user can alter the strength of seal that is provided when the second lever 10 engages with it. Referring to the example of Fig. 5, a support block 21 is attached to a first member 22 and pivotally attached, at one end, to one end of the support block 21 is a first lever 23. A second lever 24 is pivotally attached at one end to the other end of the first lever 23 and is shaped as a hook at its other end 25 so as to be engagable with a protrusion 27 on the second member 26. A spring 35 acts to bias the second lever 24 to an outwardly projecting position which flags the unlatched position of the latch as seen in figure 5. A third, cranked, lever 28 is also pivotally attached to the first lever 23 and is rotatable about the same axis 30 (provided by a pivot pin 29) as the second lever 24. The third lever 28 has a hooked end 31 which, when in the latched position (see Figure 8) engages with a lip 32 on the support block 21. The other end 33 of the third lever 28 is shaped so as to be visible through an opening 34 of the second lever 24, so that, when the latch is in the fully engaged position, the end 33 of the third lever 28 is visible and gives an indication to the user that the latch is fully engaged. When the latch is in the partially engaged position (see figure 7) , then if the third lever 28 is not fully engaged, it sits below the surface of the opening 34, and shows that the latch is not fully closed. The spring 35 is attached to the third lever 28 and the support block 21 and acts to rotate the third lever 28 toward its engaged position. To latch the latch, the two members 22,26 are brought together and the second lever 24 is pivoted outwards and over the protrusion 27 on the second member 26 (see figure 6) . The second lever 24 is then pushed towards the first member 22 so that the hooked end 25 of the second lever 24 is engaged with the protrusion 27 (see figure 7) . Pressure is then applied to the pivotally attached end of the second lever 24 and this pressure urges the hooked end 31 of the third lever 28 over the lip 32 on the support block 21, with the spring 35 acting on the third lever 28 to bring it into an engaged position. To open the latch, the third lever 28 is depressed and, at the same time, the pivotally attached end of the second lever 24 is pulled away from the second member 22. This action pulls the latch assembly back into the position shown in figure 6. As can be seen from figures 9A and 9B, the spring 35 may be connected to the support block 21 at one of a number of points, or may be a torsion spring which acts against the second lever 24, and still provide the same locking and warning functions. In the examples shown in figures 10A to IOC, the components are substantially the same as the example shown above, except for the third lever 28 which has a hooked end 36 engagable with an edge of the opening 34 in the second lever 24. In this example, as the latch is brought into an engaged position, the end 36 of the third lever 28 protrudes through the opening 34 and engages with the lever 24 to clamp the latch into position. To release the latch, the third lever 28 is pushed out of engagement with the second lever 24 and, at the same time, the second lever 24 is pulled away from the first member 22. As with the earlier example, the spring 35 is attached at one end to the third lever 28 and at the other end can be attached in a number of positions, such as on the first lever 23 or the pivot pin 29. Again, the spring 35 may be a torsion spring which, in this example, acts against the support block 21 to urge the third lever 28 toward an engaged position. The third example latch of figures 11 and 12 is similar in operation to the first example latch of figures 1 to 5, and corresponding components have been identically numbered. In this example, however, the free end of the second lever 10 is shaped so as to hook on to the component 7 when the latch is in the engaged position, so that a firmer engagement between the two members 2,6 can be provided. Also, this example provides the biasing spring 15 on the pivot axis of the first 10 and second 11 levers, simplifying the assembly of the lever as a whole.

Claims: CLAIMS 1. A latch comprising: a support block which, in use, is attached to a first member; a strike block which, in use, is attached to a second member; a first lever attached to the support block and shaped to engage with the strike block when the first and second members come into contact; a link member, pivotally attached to the support block; a second lever, pivotally attached to the link member and shaped to engage with the strike block; a third lever, pivotally attached to the link member and engagable with the support block, to retain the latch in a latched position; and, biasing means for biasing the third lever into engagement with the support block when the second lever is in its engaged position. 2. A latch according to claim 1, in which the strike block comprises two components, the first of which engages with the first lever, and the second of which is adjustably mounted on the first to provide an adjustable engagement with the second lever. 3. A latch according to claim 1 or claim 2, in which the biasing means is a spring or a combination of springs. 4. A latch according to any of the preceding claims, in which the biasing means acts to bias the second lever into a warning position when it is not fully engaged. 5. A latch according to any of the preceding claims, in which the biasing means biases the first lever towards an engaging position. 6. A latch according to any of the preceding claims, in which the first lever cooperates with the third lever to disengage it from the support block upon opening of the latch. 7. A latch comprising: a support block which, in use, is attached to a first member; a first lever, pivotally connected to the support block; a second lever, pivotally mounted on the first lever and arranged to engage a second member releasably; a third lever, pivotally mounted on the first lever, and arranged to engage the support block releasably; and, biasing means for biasing the third lever towards the position in which it engages another part of the latch when the second lever is in an engaged position. 8. A latch according to claim 7, in which the third lever engages with the support block to provide a locking function. 9. A latch according to claim 7, in which the third lever engages with the second lever to provide a locking function. 10. A latch according to any of claims 7 to 9, in which the first and third levers are mounted on a common axis. 11. A latch according to any of claims 7 to 10, in which the second lever is biased to a position in which its free end of the second lever projects outwardly from the latch. 12. A latch according to claim 8, in which the third lever is arranged so that it provides an indication to a user when fully engaged with the support block. 13. A latch according to claim 9, in which the third lever protrudes through the second lever and engages with it. 14. A latch according to any of claims 7 to 13, in which there is a common biasing means for the second lever and the third lever. 15. A latch according to claim 14, in which the biasing means is a spring, which can be attached to the support block or first lever at one end and attached to the third lever at its other end. 16. A latch according to claim 14, in which the biasing means is a torsion spring attached to the third lever and in engagement with the first lever, the second lever or support block to bias the third lever toward an engaged position. 17. A latch according to claim 8, in which the third lever is arranged so that it provides an indication to a user when disengaged with the support block. 18. A latch according to any of claims 7 to 17, in which the first and third levers are arranged so that they must be moved in opposite directions by a user when releasing the latch from its engaged position.

Inventors: BEAUCHAMP SIMON ROBERT, WRIGHT ANDREW CHARLES WALDEN, BEAUCHAMP, SIMON, ROBERT, WRIGHT, ANDREW, CHARLES, WALDEN
Applicants: BEAUCHAMP SIMON ROBERT, DZUS FASTENER EUROPE, WRIGHT ANDREW CHARLES WALDEN, BEAUCHAMP, SIMON, ROBERT, DZUS FASTENER EUROPE LIMITED, WRIGHT, ANDREW, CHARLES, WALDEN
Application year: 1994
Main classification: E05C19
IPC codes: E05C19